Patients with brain damage may experience a wide variety of consequences. Many of them suffer from disordersconsciousness, such as coma or brain death, which prevents them from interacting with the environment. The problem arises when all those people who can not speak or move are included in the same group.
"There are people who, although they show no visible sign of consciousness, can perform mental imagery tasks (ie they process information that causes and uses the senses)." These people suffer from cognitive motor dissociation and have to be differentiated "says Nicholas Schiff, neuroscientist at Weill Cornell Medicine's research department in New York.
Schiff is part of a team of researchers from several American centers who have developed a new method of assessing people in a deep state of unconsciousness, and distinguish patients who, although unable to speak, maintain their cognitive capacity at full strength. Electroencephalography (EEG) based technique is published this week in Current Biology.
Scientists believe that the way in which patients with severe brain damage are treated needs to be reconsidered. "This discovery highlights the urgent need to study and identify patients who can be" glued to their heads "and treated as unconscious," Schiff says.
"The results highlight the importance of a greater effort to improve communication with these people," he adds.
Electroencephalography is a technique of scanning the central nervous system to record real-time brain electrical activity.
Through this method, the experts analyzed how brain activity increases and decreases with the variance of sound pressure produced by speech. In addition, they calculate how long the brains of healthy people take to react with the electrical stimulus of the sound stimulus: about a tenth of a second.
According to the results, brains of patients with brain damage who maintain their cognitive function also take a tenth of a second to respond to these sound stimuli. This suggests that the mechanisms that handle speech function normally.
In order to reach these conclusions, the researchers compared the brain response of 13 healthy people to 21 patients suffering from various types of brain damage. The sample includes people with advanced vegetative status in patients with a minimal state of consciousness.
When analyzing brain activity in front of speech, healthy participants received the audience of "Alice's Adventures in the Wonderland" by Louis Carroll, while sick patients were made to listen to stories and memories of their lives before the event. injuries reported by members of his family.
Although previous research has already been able to identify people who retain their cognitive capacity in a state of unconsciousness, scientists can use this new technique to be very useful and effective as patients with brain trauma usually keep their hearing.
"By separating patients who support cognitive abilities in a particular category, we may be able to refine the results of other investigations in other contexts," Schif said.
The team of experts plans to work on developing new methods to help patients with high levels of cognitive function to improve their ability to interact with the outside world.